Add daemon utilities

daemon/daemon.go

@@ -0,0 +1,50 @@
+// Package daemon provides utilities for daemons.
+package daemon
+
+import "io"
+import "os"
+import "syscall"
+import "strconv"
+import "os/signal"
+
+// PidFile is a string that contains a path to a pidfile.
+type PidFile string
+
+// Start writes to the pidfile.
+func (pidfile PidFile) Start () error {
+	return os.WriteFile(string(pidfile), []byte(strconv.Itoa(os.Getpid())), 0644)
+}
+
+// Close deletes the pidfile.
+func (pidfile PidFile) Close () error {
+	return os.Remove(string(pidfile))
+}
+
+// Empty returns true if the object is zero value (an empty string).
+func (pidfile PidFile) Empty () bool {
+	return pidfile == ""
+}
+
+// OnSigint calls the specified function once sigint is recieved. This function
+// does not block, and spawns a goroutine that waits. For this reason, the
+// callback must be safe to call concurrently.
+func OnSigint (callback func ()) {
+	go func () {
+		sigintNotify := make(chan os.Signal, 1)
+		signal.Notify(sigintNotify, os.Interrupt, syscall.SIGTERM)
+
+		<-sigintNotify
+		callback()
+	} ()
+}
+
+// CloseOnSigint is like OnSigint, but takes an io.Closer.
+func CloseOnSigint (closer io.Closer) {
+	OnSigint(func () { closer.Close() })
+}
+
+// ShutdownOnSigint is like OnSigint, but takes an object with a Shutdown()
+// method.
+func ShutdownOnSigint (shutdowner interface { Shutdown() error }) {
+	OnSigint(func () { shutdowner.Shutdown() })
+}